1. Field of Invention
The present invention relates to a bulb having a pipe pin and a conductive wire, and a method for welding the pipe pin and the conductive wire thereof.
2. General Background and Related Art
A method for connecting a conductive wire to a pipe pin of a fluorescent lamp is disclosed in Japanese Laid Open Patent Application SHO 60-39786. Namely, the conductive wire is passed through the pipe pin. A projecting portion of the wire from a tip of the pin is cut off, leaving a predetermined length of wire projecting through the pipe pin. The predetermined portion is pushed back to the tip of the pipe pin. The pin with the conductive wire is punched at one side thereof together.
Using this method does not always result in a rigid joining of the wire and the pin. Accordingly, to better assure good joining by this method, it is necessary to use, in conjunction with the method a punching level detecting device measuring an extent of press. Such a device is described in Japanese Laid Open Patent Application SHO 61-51728. Occasionally, after being punched, the tip of the wire projects from the tip of the pipe pin. The projecting portion sometimes accidentally injures a user, such as, for example, when the lamp is being changed.
Another method for arc-welding a pipe pin and a conductive wire is described in Japanese Laid Open Patent Application SHO 60-20427. The disclosed method somewhat simplifies the processes, and prevents the tip of the wire from projecting from the tip of the pin. This method utilizes a forming process to bend the projecting tip of the wire toward one side of the pin. Though the bending portion is still welded with the pipe pin, the tip of the bending portion occasionally appears on the welding region. Accordingly, the welded pin can not be inserted in a socket. Moreover, as the bending portion is primarily welded, both the bending wire and pin can not be sufficiently connected. Furthermore, if the pin includes zinc, the zinc evaporates due to the heat of welding. Accordingly, zinc vapor sticks to an outer surface of the pin, so that the pin becomes unclean.
One aspect of the claimed inventions is directed to an improved arrangement for connecting a conductive wire and a pipe pin of a bulb construction. Another aspect of the claimed inventions focuses on an improved method of welding a pipe pin and a conductive wire which provides a simpler way of welding and a more effective resulting weld.
Another aspect of the claimed invention is directed to the bulb construction itself. The bulb comprises an airtight envelope having a filling gas therein. A conductive wire extends outwardly from the airtight envelope. This conductive wire is passed through a conductive pipe pin. A predetermined welding portion of the wire extends from the bottom of the pipe pin. A weld at this welding portion produces a smooth surface. An outer diameter of the welded portion, which is formed from melting a portion of both the predetermined welding portion and the conductive wire, is no greater than the outer diameter of the pin.
Still another aspect of the claimed invention is directed to the bulb construction itself. The bulb comprises an airtight envelope having a filling gas therein. A conductive wire extends outwardly from the airtight envelope. A conductive pipe pin has the conductive wire passed therethrough, a predetermined welding portion, and a welded portion including a smooth surface. The welded portion is formed in the pipe pin by the fluid of the melted conductive wire and predetermined welding portion flowing into the pipe pin and hardening.
Some of the claimed inventions feature a method for welding a pipe pin and a conductive wire of a bulb. The method is generally described as follows:
outwardly extending the conductive wire from an airtight envelope having a bulb base;
arranging the pin including the predetermined welding portion, to the bulb base, the pin having an outer diameter that is less than that of a pin base;
passing the conductive wire through the pipe pin with a tip of the conductive wire projecting from tip of the pin;
cutting off the tip of the conductive wire, leaving a predetermined length; and
welding the pin and the conductive wire in order to form a welded portion having a smooth surface at the tip portion of the pin.
These and other aspects of the invention will be further described in the following drawings and detailed description of the invention.